i cant set up grunt due an error

i want to create luma based theme and set up grunt for it.
path to .less files: frontend///web/css/source/style-l.less
im getting an error: unable to resolve the source file for ‘frontend///en_US/css/sourcestyles-l.less

local-themes.js below

module.exports = {
blank: {
    area: 'frontend',
    name: 'Magento/blank',
    locale: 'en_US',
    files: [
        'css/styles-m',
        'css/styles-l',
        'css/email',
        'css/email-inline'
    ],
    dsl: 'less'
},
luma: {
    area: 'frontend',
    name: 'Magento/luma',
    locale: 'en_US',
    files: [
        'css/styles-m',
        'css/styles-l'
    ],
    dsl: 'less'
},
backend: {
    area: 'adminhtml',
    name: 'Magento/backend',
    locale: 'en_US',
    files: [
        'css/styles-old',
        'css/styles'
    ],
    dsl: 'less'
},
boo: {
    area: 'frontend',
    name: 'sebu/boo',
    locale: 'en_US',
    files: [
        'css/source/styles-l'
    ],
    dsl: 'less'
}};